Marshall, Fionna, and High School
by CakeOfMischief13
Summary: Marshall is the new kid at Aaa High School and is in his freshman year. Soon after arriving, he meets Fionna, and somehow manages to fall in love with her. But with Marshall's troubled past, Fionna's overprotective twin, and the fact that Fionna already has a boyfriend, could they ever be together? High school AU. FIOLEE! Rated T just to be safe.
1. Chapter 1

**Author's Note: Hi, everybody! This is my second story, so...Yeah. Also, I am trying to think of something to say at the end of my author's notes, so review if you have an idea. Still review if you don't, though.**

 **DISCLAIMER: I do not own Adventu- You know what, I'm too lazy for this... Just read the story...**

"Marshall! Hurry up, will you? I don't want you to be late on your first day here!"

"Yeah, yeah, I know. Just a sec," Marshall said as he threw his black backpack over his shoulder. He hopped into the passenger seat of the car his mom was waiting in.

"Took you long enough," she murmured as she began to drive to Marshall's new school.

"You wouldn't have to worry about it if you got me my own car or let me drive this one."

"You're only fifteen."

"Fifteen, sixteen, same thing."

"Whatever. Anyway, this is your first day at Aaa High School. You excited?"

"Nope."

Marshall's mom glanced at her son, about to turn to him, when she remembered she had to keep her gaze on the road. "Look, I know things were pretty bad back in Nightosphere, but I promise, things will be different here. Okay?"

Marshall sighed and nodded. The rest of the car ride was silent until finally, they reached their destination. He grabbed his backpack and was about to get out of the car, when his mom stopped him. She smiled reassuringly and said, "You'll be fine, alright?"

Marshall replied with nothing more than a nod and walked to his new school. He went to the office to get his schedule and stuff like that. He looked at his schedule and saw that he had math first period. Of course, it HAD to be math. He already knew that he was going to be late, so he decided, rather than wasting energy trying to get there on time, to take his time and study the rest of the school.

Marshall stopped when he heard a voice behind him.

"Hey, are you late, too?"

He turned around to see a girl with beautiful blue eyes, wavy blond hair that reached down to her lower back, a white headband with bunny ears on it, a light blue shirt, a dark blue skirt, high socks with two blue stripes at the top, and black flats. She was also kinda chubby, but in a cute way.

"I haven't seen you around before, you new?" she asked as she smiled sweetly. Marshall just nodded. He was doing a lot of that today. "My name's Fionna," she stated while holding out her hand for him to shake.

The corner of his mouth twitched as if he was about to smile but decided against it. He took Fionna's hand in his and shook it. "Marshall."

"Nice name. So, where you heading?"

Marshall said nothing in response, instead he just handed her his schedule. Fionna looked at it. "Math, huh? Coincidentally, I was going there myself. Let's go." she said, excitedly. So, to math class they went.

They didn't get to talk much in there, considering their seats were four desks apart. The rest of Marshall's classes just ran by. He occasionally ran into Fionna in the hall, and they talked a little.

Eventually, it was lunch time, and Marshall was putting his stuff away in his locker, when Fionna came up to him. "Hi, Marshall! Wanna eat lunch with me me and my friends?" she asked in that happy voice of hers. He shrugged. "I wasn't going to give you a choice, anyway." With that said, she dragged Marshall to lunch.

Once they both got their food, they sat down at Fionna's table. Soon, a boy with a white hat with bear ears and an appearance similar to Fionna's sat down across from her. "Hey, Fi, who's this guy?" he questioned, gesturing to Marshall.

"New kid. His name's Marshall," she then directed her attention to said boy, "Marshall, this is my twin brother, Finn."

Marshall waved in a greeting.

Another boy with a red and orange mohawk and brown eyes walked over to the table and sat next to Finn. He looked at Marshall questionably. Fionna noticed this and quickly answered his silent question. "FP, this is Marshall, he's new here," she turned to Marshall, "This is Flame Prince. We call him that because he likes to light stuff on fire. We call him FP for short." Marshall, once again, waved his greeting.

Fionna managed to start a little bit of small talk, until yet another boy arrived. He had pink hair and was clothed from head to toe in pink. His eyes were an almost purple blue color. Fionna immediately got up to greet him and kissed him full on the lips. "Marshall, this is Bubba, but we all call him Gumball. He's my boyfriend."

 **Author's Note (Two!): This chapter's kinda short, but I promise they'll get longer. Also, I'll try to update once a week. Please follow, favorite, and review!**


	2. Chapter 2

**A/N: Hey, people! I don't know if you noticed, but there is now a cover photo for this story. It was drawn by yours truly, so tell me what you think of it. I don't think I did a good job on Fionna, but I'd say Marshall was actually one of my greatest accomplishments in art. Italics are thoughts, by the way. Anyway, sit down snd shut up as I continue to tell you the tale of Marshall, Fionna, and High School.**

If Marshall was drinking something, he probably would've spat it out all over the table. He just couldn't believe that this guy was Fionna's boyfriend. _Of course, of all people it had to be pinky. Stupid Gumbutt..._

Fionna sat back down and Gumball quickly sat next to her. They began to whisper amongst themselves, giggling like misfits and occasionally glancing at the others. Marshall sighed and picked at his food, or at least what he assumed was food. Although, he wasn't too sure; it looked like it was _breathing..._ He shuddered, not wanting to think about what the mysterious "meal" could be, and pushed it away.

Finn noticed this and, with a mouth full of the... stuff, asked, "Are you gonna eat that?" Marshall shook his head. "Cool, thanks," he said while taking the "food" and stuffing it in his mouth.

"You actually eat that?" Marshall asked, scooting away slightly as he did so.

FP chuckled. "None of us understand how he can willingly eat that. It's best to bring real food from home. I'll share some of mine with you if you want." He offered a granola bar while saying this. Marshall shook his head. "You sure? You'll probably be hungry later." FP stated. Marshall nodded. FP shrugged. "Alright."

Soon, lunch ended, and they all had to go to their next classes. Fionna found Marshall in the hallway, and they found out they both had history next, and every single class after that. In history, they got to sit next to eachother. Because of this, they ended up talking the entire time. It wasn't really anything important, they were just joking around and having fun. Although, every time Fionna tried to find out why Marshall moved, he avoided answering the question and immediately changed the subject. Of course, this just peaked Fionna's curiosity, and she swore to herself that she would find out by the end of the school year. Fionna, knowing that if she was going to find out, she'd need to spend as much time as possible with him, decided to invite him to her house after school. Marshall accepted.

After school, they went to Fionna's house. As soon as they arrived, a white and yellow cat with blue eyes lept at Marshall, hissing wildly. Marshall stepped to the side, avoiding it, causing the cat to hit the wall behind him. Fionna quickly grabbed the cat. "This is Cake, my cat. Sorry about that, she's usually pretty friendly," She looked at Cake, "Cake, this is Marshall. Say hi." Cake just hissed at him and scampered off. Fionna shook her head and turned her attention back to Marshall. "Sorry about her." Marshall smiled slightly and shrugged. "You don't talk a lot, do you?" Another shrug.

Fionna was about to respond, when Finn randomly appeared behind them. "So, what are you two talking about?"

"Nothing, Finn, go away," She said while shoving him.

"But, what if I want to stay?"

"Finn..."

"Come on, Fi..."

Fionna just gave him a death glare.

"Fine, fine, I'm going." Finn walked off as he said this. When he was out of sight, Fionna turned back to Marshall.

"Anyway, why did you move here?" She asked, innocently.

Marshall got a distant look in his eyes, before he shook his head, as if he was trying to shake whatever he was thinking of out of his head. He tried to think of something to get her off the subject. He spotted Finn staring at them, attempting to listen to their conversation. "Your brother's trying to spy on us," He informed.

Fionna swiftly turned around, "Dammit, Finn! Leave!"

"Alright, fine, I'm actually going this time." He walked away and into his room.

Fionna sighed, "I hate him sometimes." She turned back to Marshall, only to find him in the living room, looking through the video games. He stopped when he saw Mortal Kombat.

He held it up and asked, "Can we play?"

Fionna grinned. "Yeah, sure. Just be prepared to get your butt kicked!"

She put the game in and they both grabbed the controllers. Fionna picked Kitana and Marshall picked Noob.

Three battles later, Fionna cried out in frustration as Marshall beat her... AGAIN. "No fair! You cheated!"

"Care to explain how I cheated?" He replied, smirking.

"You just did! Shut up!" Suddenly, a smile spread across her face. "How about on this next round, we make a bet?" Marshall tilted his head as she continued, "Whoever loses has to answer any question the winner asks."

Marshall shrugged, "Alright. Prepare to die, again."

Marshall stared in shock at the screen. Fionna had just gotten a flawless victory with seemingly no effort. "But... How..? I... You... Damn. So, what do want to ask?"

Fionna immediately asked, "Why did you move?"

 _Crap. So this was what she was planning... Clever girl. But I can't tell her, yet I'd feel guilty lying to her... Can I avoid it, again? No. I did agree to the bet. Something please save me..._

Marshall phone went off, signaling he got a text message. He checked it, and saw it was his mom. _Thank god..._ "I have to go." He automatically got up and went to the door, about to go when Fionna stopped him.

"Marshall, please," She begged, staring at him with the most adorable puppy eyes she could manage.

He stared blankly at her for a while, before he sighed. "Maybe. I'll think about it." _Seriously, Fionna, why can't I say no to you?_ He went out the door and walked back to his house.

 **A/N (2!): Heck yeah! I managed to get this to more than a thousand words! Yes!**


	3. Chapter 3

**A/N: Hello, and welcome to the 3rd chapter! (Yay...) Anyway, sorry it took a while to get this up, I had some writer's block. I know, it's a bit early to have writer's block, but...whatever...**

The next morning, Marshall, to say the least, did not want to get up. He knew that as soon as he went to school, that cute little bunny, Fionna, would be begging him to tell her about...

He sighed at the thought of Marceline. She was far too young to leave this world, and it was all his fault, too. He promised to protect her, **promised**. A pinky promise, her favorite kind. If he had done something, anything, she could've been here with him. She could've smiled and laughed with him, day after day. She could be his little sister, again.

Marshall was quickly drawn out of his thoughts by his mom's voice, calling him for breakfast. He rolled out of his bed, face planting onto the floor. He got up and threw on some clothes, before he stumbled to the kitchen.

On the table, there was a bowl of cereal, Count Chocula to be exact, two pieces of toast, both with strawberry jam on top, and some orange juice. Marshall sat down and began to eat, when the school lunch crossed his mind. He turned to his mom and, with a mouthful of food, asked, "Hey, mom, can I pack my own lunch?"

She responded with a nod and a simple, "As long as I don't have to make it."

After he finished his breakfast, Marshall made and packed his lunch, grabbed his backpack, and went into the car with his mom. Upon arriving, he was almost immediately greeted by Fionna.

"Come on, Marshall! I won, fair and square, now you have to tell me," she said, crossing her arms.

Luckily, Marshall had been thinking of loopholes for the bet in the car. "Technically, you just said that I had to tell you. You never made any time range of when I have to tell you. Therefore, I just have to tell you some day, but not now."

"But you said you'd tell me today."

"Yesterday, I said maybe, not yes."

"But, Marshy..."

Marshall froze. Marshy... Marceline always called him that. Poor Marceline... Her blood, it's on his hands. He could've saved her. He could've went instead. But, no, she was dead, her blood was spilled, and it was all his-

"Hey, are you okay? You haven't said a word for a couple of minutes."

Marshall blinked. Once. Twice. He slowly turned to meet Fionna's concerned eyes. "I... I'm fine, I was just, um, thinking." He cursed his lame excuse, knowing she was going to look for more detail. And that she did.

"What were you thinking about?" She tilted her head while saying this, hoping to get something out of him.

To her disappointment, he only answered with a shrug.

"Please..."

He shook his head.

"Fine." After about a minute of silence, Fionna spoke up, again, "Hey, Marshall?" Marshall turned his head to her to let her know he was listening. "Promise you'll tell me why you moved here? It doesn't have too soon, just sometime by the end of the year... Please?"

Marshall turned his full attention to her. _Oh, great, she has those eyes again. Those cute, adorable, completely irresistible, blue, beautiful puppy ey- wait! Beautiful? Are you kidding me? Marshall Lee Abadeer! You just met Fionna yesterday! You can't think of her like that! Besides, she's already with Gumbutt... Stupid son of a-_

"Um... Earth to Marshall," Fionna waved her hand in front of his face as she said this, breaking him out of his trance.

"Hm? Um, yeah, yeah, I promise."

"Pinky promise?"

A pinky promise. Marceline's favorite type of promise, the only promise she ever considered. And, of course, because of this fact, Marshall dove straight into another unwanted trance, flashbacks of the young girl sprinting through his mind.

"...shall? ...Marshall!" Fionna exclaimed, grabbing his shoulder and shaking him slightly. Marshall blinked a couple of times, before staring blankly into her eyes. "Are you alright? I've been calling your name for a while, but you didn't react at all."

He nodded, "I'm fine."

Fionna couldn't help but notice he still seemed a little distant. Slowly, almost hesitantly, she asked, "Are you sure?"

"Yes, I'm sure! I'm fine, Fionna!" he snapped.

Fionna shrunk back slightly, murmuring a small apology. Seeing this, Marshall sighed and lowered his voice to a softer tone, "Sorry, Fi, it's just... Forget it. I promise I'll tell you about it sometime by the end of this year."

"Pinky promise?"

He sighed, once again, but managed to stop himself from zoning out. He nodded. "Pinky promise."

 **A/N (2!): When will Marshall tell her? How did little Marceline die? Why am I asking questions I already know the answers to? ...Wait! Why am I asking questions in the first place? ...Well, I guess the world may never know... Anyway, hope you liked this chapter! Please follow, favorite, and review!**


	4. Chapter 4

**Hey, everyone! So, I know I told a couple people I would update soon, but I was feeling kinda lazy, and when I was ready to write this chapter, my tablet stopped working. Then when it started working again, the internet on it wasn't working. And then, I got an idea for a Hotarubi no Mori e fanfic, and that was all I could think about. The internet started working a while ago, and I was really excited to write the Hotarubi no Mori e fanfic, but I remembered this, and decided, "I'm gonna freaking do this!" So... yeah. That concludes this excuse. Does anybody even read these?**

 **Fionna's POV**

It has been a week and two days since Marshall got here. All nine of those days we've hung out, five of which we played Mortal Kombat. I'll admit, he's getting better, but I still win... Most of the time. The other four days, we went to a skate park, watched some horror movies at my house, went to a coffee shop that's right by the school, and pulled some pranks on Finn. Today, we were planning on having another horror movie marathon, as soon as English was over. Oh, yeah, did I mention we're in English? Well, we are, and it should be ending in three... two... one...

...

I'm gonna try that, again... It should be ending in thr-

*RRRRRRRRRRRRRIIIIIIIIIIIIINNNNNNNNNNNNNGGGGGGGGGGGG*

Finally! Freedom!

I grabbed my stuff and started walking out, Marshall following. When we walked out into the hall, I turned to him and said, "Meet me at my locker, okay?" He nodded and I walked to my locker.

I opened it and grabbed my green backpack, shoving all my stuff inside it. I stopped, however, when I heard a voice behind me. "Hello, Fionna." I turned around to see Gumball. I smiled as an invitation for him to continue. "I was wondering if you'd like to join me for some ice cream?"

My smile faltered a bit. "I would love to, but," he gave a small frown, "I was gonna hang -"

"Out with Marshall?" He finished. I managed to find some annoyance in his tone.

"Well... yeah," I replied, a little unsure.

He sighed, "Fionna, you have been hanging out with him ever since he got here. I just want to sp-"

We both heard a small cough. I turned to see Marshall standing, awkwardly. I looked back to Gumball to find him glaring at Marshall, who was casually staring back. The air around us was starting to get tense, and I decided I wanted to get out of it as soon as possible.

"Anyway, Gumball, we gotta go, so we'll talk about this later. Love you, bye!" I said as I grabbed Marshall and dragged him away.

 **Gumball's POV**

Stupid Marshall. Stupid Marshall. Stupid Marshall. Stupid Marshall. Stupid Marshall. Stupid Marshall. Seriously, I can't believe that guy. Trying to take Fionna away from me. That bastard. And he acts so innocent about it, too. I know he knows what he's doing. But I won't let him win. Soon, Fionna won't even want to spare a glance in his direction. All I need to do is put my plan into motion, and Marshall will be out of the picture.

 **I know it's kinda short, but I really want to start writing the other fanfic, and, you know, I promised myself I wouldn't start writing it until I finished this chapter, so... Yeah. Anyw-**

 **Marshall: Hey, 42MischievousCookies, or whatever your name is!**

 **What?**

 **Marshall: Why is Gumball such a di-**

 **Fionna: *comes up behind Marshall and puts her hand over his mouth* Jerk. Remember, Marshall, in the author's notes, you can't use cuss words.**

 **Marshall: *muffled* Ugh... Fine. Can you take your hand off now?**

 **Fionna: *takes hand off***

 **Hey, um, could you go? You're kinda making the author's note longer than the actual chapter.**

 **Gumball: Yeah, and I don't really appreciate you two calling me a jerk.**

 **Gumball?! I never gave you the key to the author's note! How did you get in?!**

 **Gumball: You left the door unlocked.**

 **Oh...**

 **Fionna: Um... Hi, Gumball... How long have you been here..?**

 **Marshall: Does it matter? In the next author's note, he won't rememb-**

 **EVERYBODY GET OUT! YOU'RE MAKING THIS WAY LONGER THEN IT SHOULD BE!**

 ***Marshall, Fionna, and Gumball all walk out***

 **Sorry about that...**

 ***sighs and walks out, shutting the door behind me, muttering to myself***


	5. Chapter 5

**IMPORTANT! PLEASE READ: Hey... So, you guys are gonna hate me for this, but I'm not gonna continue this... Please don't kill me! I am going to rewrite it completely, however. It will basically be the same plot, but a couple things will be changed. The first chapter will probaby be published in... I don't know. A month, at most... Yeah. Keep an eye out for it. Heheh... I'm gonna go, now... So, yeah, see ya!**


End file.
